Agricultural harvesting machines such as combine harvesters generally are developed to handle a large variety of crops. For example a combine harvester may be used to harvest small grain crops such as wheat and rye, rape or grass seed or large grain crops such as peas or corn. In this manner the use of the harvester, which is a high investment tool, can be extended over a longer season.
Conventionally the harvester is equipped with a detachable crop collecting attachment, such as a grain or corn header, which cuts the stems of the crop standing in the field and conveys the same to the inlet of an elevator housing. Alternatively crop which has been cut previously can be lifted up from the field by a pick-up attachment and conveyed to the same inlet. Elevator mechanism, commonly a chain elevator with transverse slats, grab the collected crop deposited in front of the inlet and convey it rearwardly and upwardly towards the crop processing mechanism, conventionally a threshing drum and concave or grate assembly.
As illustrated by U.S. Pat. No. 3,758,472, the crop usually is engaged by the lower run of the chain elevator to transport it along a bottom plate of the elevator housing. The upper run is shielded from the lower run by a backing plate which extends between the front and rear transverse shafts of the elevator. This plate reduces the chances that material which was not removed from the elevator by the threshing system, falls back on top of the lower run and gets lodged between the chains and the sprockets driving the chains near the exit of the elevator. The backing plate equally provides additional support for the upper run of the chains.
The front shaft may also be provided with dedicated anti-wrapping mechanism as shown in DE-U-92 05 617. Herein a set of curved plates is mounted over the front shaft of the elevator, between the elevator sprockets. These plates do not constitute a closed surface: triangular openings are provided behind the sprockets for allowing passage of the sprocket teeth and of any material which got trapped between the teeth. However crop material can enter through these openings and accumulate in the area around the shaft. Eventually this material will wrap around the shaft and start impeding its rotation.
Hence there is a need for an elevator structure which effectively keeps stray crop material from wrapping around the shaft without restraining the rotation of the sprocket teeth.